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[afro-nets] Mosquito and Malaria Control (43)
- From: "Peter Burgess" <email@example.com>
- Date: Wed, 19 Jul 2006 12:38:22 -0400
Mosquito and Malaria Control (43)
Sorry this is rather long ... but it is a big subject.
I would like to follow up on a message that Chris White sent last September about Mosquito/Malaria Control. Chris made the point that interventions that are used in the United States are wrong for Africa ... but in all honesty, I don't think he made a strong case for this.
The discussion had talked about the use of aerial spraying in the USA in the aftermath of the Katrina hurricane ... and he correctly pointed out that this was not spraying against malaria, but against various other mosquito borne diseases (yellow fever, dengue and west nile virus). Since malaria has not been a problem in the area since around 1950, spraying against malaria is not done ... which seems to make sense! My conclusion is that aerial spraying is a very appropriate and cost effective way of delivering anti-mosquito pesticide, especially with modern understanding of pesticide and the use of ultra low volume (ULV) technology. I have made some cost estimates for aerial treatment and it is very low cost per acre ... and depending on population density can be very low cost per capita of human population.
Chris talks about the mosquito (specifically anopheles gambiae s.s.) breeding in all sorts of small, transient rain-fed pools ... and how it is unrealistic and uneconomic to expect that larvaciding can be effective. I am not at all sure that Chris is right. From a practical scientific point of view, larvaciding works ... though it is difficult to organize over a big area. I don't think this problem is insurmountable, though it must not be ignored. Arguably cleaning up the environment and larvaciding is the best way to break the cycle of mosquito population rebuilding. Building the Panama Canal 100 years ago was done in the face of virulent malaria, in large part by cleaning up the environment where the work was going on and where workers were living. Spatial information seems to suggest that not all water has the same breeding performance.
I have not been able to find much cost and result information that convinces me that insecticide treated bednets is the best way to go for effective mosquito malaria control interventions. While an individual seems to get less malaria when they use a bednet ... the cumulative experience in the community does not seem to change very much. This may not be the right conclusion, because the information available is not very clear. Rather than having a focus on costs and results (as measured by reduction in the prevalence of malaria in the community), much of the cost performance information relates to merely the cost and the scale of distribution of bednets into the community ... an interesting metric, but not a metric that helps determine the effectiveness of bednets as an anti-malaria intervention. I think it is fair to conclude that bednets on their own do not make much of a difference, even when they are widely distributed. I would love to know more about costs and reduction in malaria parasite prevalence using the bednet approach.
There seems to be a lot of information that shows that interior residual spraying (IRS) does have a significant impact on the prevalence of malaria in the community ... and especially when DDT is used as the pesticide. The cost of a large scale IRS program is substantial, but the results seem to justify the expenditure, especially if DDT is permitted. Sadly use of DDT in a country has the possibility of creating trade issues with Europe, not so much because of prevailing legislation but because of corporate environmental sensitivities and concern that there might be adverse consumer impact.
The role of medical interventions is not insignificant. Remove the parasite from the human host and malaria transmission will be reduced ... though it is not easy to get the reduction in malaria transmission low enough so that the parasite population gets reduced. It can be done ... but it is not the norm for Africa at the moment.
Clearly resistance is an issue in any chemical intervention ... whether against the mosquito or the malaria parasite. A modern management information system for any intervention should take this into consideration and collect appropriate data and use it to manage the interventions.
Lastly ... the information I have been able to collect seems to suggest that a variety of interventions going on together and coordinated gives the best results at least cost. A data driven program, including spatial information about all the interventions and all the results can be used to keep costs down and to deliver better than "average" results. But in order for data to be useful, they must be organized as "management information" for decision making and not merely to satisfy academic criteria.
I would love to get more information that will help move me along in the design of an integrated mosquito malaria control model ... and a program that can be helpful in Africa to optimise mosquito and malaria control interventions.
Transparency and Accountability Network